Platform API: demoUrl from latestVersion returns broken sandbox preview (GENERATING is not defined)

[bogris]

When using the Platform API to retrieve chats via v0.chats.find(), the
latestVersion.demoUrl field returns a vusercontent.net URL that fails to render
with:

ReferenceError: GENERATING is not defined

This affects chats created after the February 2026 sandbox update. Older chats’
demoUrl still render correctly when embedded in an iframe.

Reproduction:

1. Create a chat via the Platform API (or use a recently created one)
2. Read latestVersion.demoUrl from the response
3. Open the URL in a browser or embed it in an iframe
4. The page is blank with GENERATING is not defined in the console

Expected: The demoUrl should render a working preview of the generated app, as
documented in the SDK examples.

Environment:

• v0-sdk@0.16.1
• Embedding via iframe with sandbox=“allow-scripts allow-same-origin
  allow-modals allow-forms allow-popups”

Context: We’re building a tool that lists projects/chats via the Platform API
and embeds their previews. Older demoUrl values work fine — this only affects
chats created after the recent sandbox infrastructure change.

For the same project, the preview works correctly in the V0.dev native UI.

[system]

Hey! To help debug your v0 project, could you share your v0 chat link?
It looks like https://v0.app/chat/... — you can copy it from your browser’s address bar while in the chat.

You’ll also need to unlist the chat so our team can view it — here’s how: Sharing | v0 Docs

This helps the team reproduce what you’re seeing much faster. Thanks!

[francois-lassl (Francois)]

Same Here:
Its unlisted

Private Chat - v0 by Vercel

What would be the best approach here? Waiting until its fixed does not feel like the right choice. should we change the architecture to a VM and run the files there and expose our own preview url?

[pawlean (Pauline P. Narvas)]

I don’t see the same error. Have you tried duplicating the chat?

[pawlean (Pauline P. Narvas)]

I actually see it loading fine

[danielmauch (DM)]

I have same Problem

[francois-lassl (Francois)]

@pawlean Thanks for the response. the issue is that the demoUrl of that chat which I get over the API (chat.latestVersion.demoUrl) throws this error

This is the demoUrl of that chat, which I get over the API:

...
"latestVersion": {
    "id": "b_lVxZl9xnC05",
    "object": "version",
    "status": "completed",
    "demoUrl": "https://demo-kzmovlc86d22tz1mk1th.vusercontent.net?__v0_token=eyJhbGciOiJkaXIiLCJlbmMiOiJBMjU2R0NNIn0..EdHhtX9xkHlNPGOH.ogWbls2BV4Ozr1nPhK2S3v2MSBndd67wNeCXjLxWJ_jj1JR8pVPvGI-Hps7eM_svzd0r9oxvEAAunuDDKL5MwOz2f_cEWCL5xUD6XHOR4qL3Qh7PzG_EU-00Y7fhjYclD8lvuKhlx2sk8qWAcRWxiwdAAQkQGsgsCkaRJ9LrTnCXdwohoWZ-V6ede6-H9fPjDjAtqyz8oQe5wW_8v3huOYSuOpYIBA.TqE5X367YWd9loS8ksInQg&__v0_vercel_project_id=prj_XmbjiL0unOoaUS2RzYQeRSJRHl1G",
    "screenshotUrl": "https://api.v0.dev/v1/chats/gwkIimRcLrP/versions/b_lVxZl9xnC05/screenshot",
    "createdAt": "2026-04-14T08:59:03.745Z",
    "updatedAt": "2026-04-14T09:50:00.188Z",
...

Over the UI of v0.app I see everything fine.
If I go to Open in new Tab

I see that the url form the UI of v0.app is not the same as the one I get over the API

so the one i get over API

v0

Is not working (GENERATING Error) and can’t be displayed in an iframe (shows blank)
And is also different that the one exposed over v0.app/chat/button-id-generation-gwkIimRcLrP
(this one https://vm-v0bwsuoni0dkl29jlzl8h9.vusercontent.net/, which des work)